High definition video extender and method

ABSTRACT

An apparatus and method for extending high definition multimedia signals from a source to a display over long distances (e.g., up to 300 feet) using a single cable medium having a plurality of twisted pair conductors contained therein. The extender transparently supports HDMI and/or DVI signaling, which allows encrypted video content to be displayed at the remote display (or other sink device). Display data channel control (DDC) information is sampled and transferred in packet from the local unit to a remote unit to comply with high-bandwidth digital content protection (HDCP).

RELATED APPLICATION DATA

The present application is a continuation of U.S. patent applicationSer. No. 13/079,178, filed on Apr. 4, 2011, now U.S. Pat. No. 8,776,163;which is a continuation-in-part of U.S. patent application Ser. No.13/027,996, filed on Feb. 15, 2011; the disclosures of which are bothincorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus and method for extendinghigh definition multimedia signals from a source to a display over longdistances using a single cable medium having a plurality of conductors.

DESCRIPTION OF THE RELATED ART

The digital visual interface (DVI) and the high definition multimediainterface (HDMI) are two common audiovisual standards for transmissionof high definition video signals. DVI and HDMI define communicationinterfaces and protocols that are used to transport audio, video, andmanagement information between audiovisual devices. The DVI or HDMIsignals can be communicated via a single multimedia cable havingisolated signals from an audiovisual device such as a DVD player, acable box, etc. to another audiovisual device such as a televisionand/or display. HDMI and DVI interfaces use TMDS (Transition MinimizedDifferential Signaling) to send video data from a source to a display.Thus, the video data is generally compatible between the two standards,which means that an HDMI enabled television can display video from a DVIenabled source and vice versa. HDMI, however, additionally encodesdigital audio data that cannot be extracted by a DVI display.

For purposes of this application, the remainder of the disclosure willfocus primarily on the HDMI interface, but the scope of the claimsincludes DVI and HDMI signals, unless specifically excluded.

HDMI is a proprietary all-digital audio/video interface capable oftransmitting uncompressed video streams. HDMI features generally includethe capability to transmit billions of colors, variable high definitionscreen resolutions and high refresh rates for smooth motions sequences.HDMI also includes multi-channel digital compressed and uncompressedaudio. The digital audio and video data transported using HDMI istransmitted electrically using a TMDS interface that is capable ofsending high speed data with low noise. HDMI further includes devicemanagement control through two separate management buses: the consumerelectronics control (CEC) bus and the display data channel (DDC) busbased on part of the inter-integrated circuit (I²C) bus. The DDC bus maybe used for product identification and authentication of copyrightedmaterial before the video information is transmitted, while the CEC busmay allow a single remote control module to control multiple HDMIdevices within a CEC bus chain. The primary medium used to transmit theHDMI information is copper wires that can drive the HDMI signals for alimited distance. HDMI devices are generally either sources of HDMI dataor sinks of HDMI data. HDMI data is generally transferred from a sourceto a sink.

HDMI is compatible with HDCP (High-bandwidth Digital Content Protection)digital rights management technology. HDMI provides an interface betweenany compatible digital audio/video source, such as a set-top box, aBlu-ray DVD player, an HD DVD player, a PC, a video game console or anAV receiver and a compatible digital audio and/or video monitor, such asa digital television.

The HDMI interface was developed to transport high-speed digital videosignals over relatively short distances using special HDMI cables. Asthe distance increases, the quality of the video degrades rapidly andthe cost of the cable increases dramatically. Transmittinghigh-definition video over long distances without degrading the qualityof the video signals is challenging and important, especially over ashielded or unshielded Ethernet cable, which is widely available andwell accepted as a standard communication medium.

SUMMARY

Aspects of the invention relate to an apparatus and method for extendinghigh definition video signals from a source to a display over longdistances using a single twisted pair cable.

An extender for extending high definition multimedia signals over asingle twisted pair cable medium having a plurality of twisted pairconductors, the extender includes: a local unit having: a first localport for receiving high definition multimedia signals from a highdefinition video source, wherein the high definition multimedia signalsinclude a plurality of video signals and at least one control signal; asecond local port for receiving an associated twisted pair cable mediumhaving a plurality of twisted pair connectors; local circuitry forconverting the high definition multimedia signals to a plurality of

differential video signals and at least one differential data displaychannel (DDC) signal, wherein the DDC information includes serial clockand serial data that is sampled and transmitted in packet form at a ratesufficient to comply with high-bandwidth digital content protection(HDCP) and wherein the local circuitry is operable to transmit andreceive the DDC information as a differential common mode signalcorresponding to at least two of the plurality differential multimediasignals out the second local port over the associated twisted pair cablemedium; and a remote unit having: a first remote port for receiving theassociated twisted pair cable medium, wherein the remote unit receivesthe plurality of differential multimedia signals and the differentialcommon mode signal output from the local unit; remote circuitry operablefor converting the plurality of differential multimedia signals intoseparate high definition multimedia signals at the remote unit andconverting the differential common mode signal received at the remoteunit to provide control information to the remote unit to comply withHDCP; and a second remote port coupled to the circuitry for outputtingthe high definition multimedia signals to a display device.

Another aspect of the invention relates to a method for extending highdefinition multimedia signals over a single twisted pair cable mediumhaving a plurality of twisted pair conductors, the method including:receiving a plurality of differential multimedia signals from a sourceat a local unit, wherein the plurality of differential multimediasignals include a plurality of video signals and a clock signal;transmitting the plurality of differential multimedia signals and datadisplay channel (DDC) information to a remote unit, wherein the DDCinformation includes serial clock data and serial data that is sampledand transmitted in packet form at a rate sufficient to comply withhigh-bandwidth digital content protection (HDCP) and the DDC informationis transmitted as a differential common mode signal corresponding to atleast two of the plurality differential multimedia signals; receivingthe plurality of differential multimedia signals and the DDC informationat a remote unit; transmitting DDC information from the remote unit tothe local unit; outputting the plurality of differential multimediasignals high definition multimedia signals from the remote unit to anassociated display based at least in part on the control information.

Other systems, devices, methods, features, and advantages of the presentinvention will be or become apparent to one having ordinary skill in theart upon examination of the following drawings and detailed description.It is intended that all such additional systems, methods, features, andadvantages be included within this description, be within the scope ofthe present invention, and be protected by the accompanying claims.

It should be emphasized that the term “comprise/comprising” when used inthis specification is taken to specify the presence of stated features,integers, steps or components but does not preclude the presence oraddition of one or more other features, integers, steps, components orgroups thereof.”

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other embodiments of the invention are hereinafterdiscussed with reference to the drawings. The components in the drawingsare not necessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. Likewise, elementsand features depicted in one drawing may be combined with elements andfeatures depicted in additional drawings. Moreover, in the drawings,like reference numerals designate corresponding parts throughout theseveral views.

FIG. 1 is an exemplary illustration of a system for extending highdefinition multimedia signals in accordance with aspects of the presentinvention.

FIG. 2 is a schematic block diagram illustrating an exemplary local unitin accordance with aspects of the present invention.

FIG. 3 is a schematic block diagram illustrating the use of common modevoltage to exchange information between the local unit and the remoteunit in accordance with aspects of the present invention.

FIG. 4 is an exemplary method for controlling DDC signaling inaccordance with aspects of the present invention.

FIG. 5 is a schematic block diagram illustrating an exemplary remoteunit in accordance with aspects of the present invention.

FIG. 6 is a schematic block diagram illustrating a second exemplarylocal unit in accordance with aspects of the present invention.

FIG. 7 is a schematic block diagram illustrating a second exemplaryremote unit in accordance with aspects of the present invention.

FIG. 8 is an exemplary method in accordance with aspects of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the detailed description that follows, like components have beengiven the same reference numerals regardless of whether they are shownin different embodiments of the present invention. To illustrate thepresent invention in a clear and concise manner, the drawings may notnecessarily be to scale and certain features may be shown in somewhatschematic form.

Aspects of the invention relate to an apparatus and method for extendinghigh definition multimedia signals from a source to a sink over longdistances using a single cable medium having a plurality of twisted pairconductors contained therein. In general, a video (e.g. HDMI, DVI)extender is disclosed that distributes high resolution HDMI or DVI videoto a display or other sink device up to a long distance away from thesource via a single cable medium (e.g., a Category 5, 5e, 6, 7 cable orthe like). Additionally, the extender provides support for digital audioembedded in the HDMI/DVI link, as well as infrared and othernon-HDMI/DVI data. The extender 10 transparently supports DDC and HDCPsignaling, which allows encrypted video content to be displayed at theremote display (or other sink device). Support for an IR extensionprovides the ability to control the source while the user is at or nearthe display, which may be separated from the source a distance ofhundreds of feet, as discussed below.

Referring to FIG. 1, an exemplary system 10 in accordance with aspectsof the present invention is illustrated. The exemplary system 10includes a source of high definition video signals 12, a first coupler14 for coupling the source 12 to the local unit 16, a cable medium 18for coupling the local unit 16 to a remote unit 20 and a second coupler22 for coupling the remote unit 20 to a sink 24. The distance betweenthe local unit 16 and the remote unit 20 may be any desired distance.Due to performance issues, the distance between the local unit 16 andthe remote unit 20 is generally less than about 500 feet, and preferablyless than about 300 feet. One of ordinary skill in the art will readilyappreciate that the distance between the local unit 16 and remote unit20 is provided for illustrative purposes and not intended to limit thescope of the present invention.

The source of high definition multimedia signals 12 may be any suitablesource of high definition multimedia signals. For example, the source 12may be a DVD player, HD DVD player, Blu-ray player, a cable TV set-topbox, a satellite TV set-top box, a computer, etc. The source of highdefinition multimedia signals may output HDMI and/or DVI compliantsignals. Generally, the source 12 will output high definition multimediasignals in the form of four differential signals (three digital videosignals and one clock signal).

The first coupler 14 is terminated at a first end 14A to match theexpected output from the source 12. The coupler 14 may also beterminated at a second end 14B to match the expected input port 40 ofthe local unit 16. Generally, the coupler 14 is terminated at the firstend and the second end with identical connectors, although theconnectors on the first end of the coupler may have a different type,form and/or configuration than the connector on the second end ofcoupler 14. The coupler 14 may take any desired form. Exemplary couplers14 may include an HDMI cable or a DVI cable, for example.

Referring to FIG. 2, the output of the source 12 includes fourtransition minimized differential signals (TMDS), which are commonlyreferred to as D0, D1, D2, DCLK (also referred to herein as multimediasignals 26). The D0, D1 and D2 signals contain data related to videosignals and the DCLK signal is a clock signal. A bi-directional displaydata channel (DDC) signal 28 is also output from the source 12 oncoupler 14. As stated above, in HDMI systems, devices can generally beeither sinks or sources of data. The DDC signals 28 can be used by anHDMI source (e.g., source 12) to discover the configuration and/orcapabilities of a HDMI sink (e.g., display 24). A bi-directionalconsumer electronic control bus (CEC) signal 30 is also output from thesource 12 on coupler 14. The CEC bus 30 provides high-level controlfunctions between HDMI devices. For example, in one embodiment, the CECbus 30 allows for a single remote control module to control multipleHDMI devices within a CEC bus chain. A +5V signal 34 may also be outputfrom source on coupler 14. This signal may be used to indicate to thesink that a source is connected and powered on. A hot-plug signal may beoutput from the local unit 16 to the coupler 14. This signal may be usedto indicate to the source 12 that the sink 24 is powered on andconnected to the remote unit 20 providing that local unit 16 and remoteunit 20 are connected via cable 18 and powered on.

The output of the coupler 14 is connected to the local unit 16 at port40. A schematic block diagram of an exemplary local unit 16 isillustrated in FIG. 2. The TMDS multimedia signals 26 are routed fromthe port 40 to a driver 42. The driver 42 may be used to modify one ormore physical characteristics of the TMDS multimedia signals 26. Forexample, the output of the driver 42 is source-terminated with a 50 to100 ohm pull-up resistor (not shown). In addition, the driver 42 offersthe ability to add levels of pre-emphasis or de-emphasis as well asinput equalization (re-timing) to the TMDS multimedia signals 26. Forexample, the amplitude of the multimedia signals may be modified and/ora pre-emphasis may be applied to the multimedia signals to increase riseand fall times that are reduced during transmission across longdistances.

An exemplary driver is the Pericom PI2HDM1412AD, which is manufacturedby Pericom Semiconductor Corporation of San Jose, Calif., or EL9131manufactured by Explore Microelectronics, Taiwan. These drivers areidentified for illustrative purposes only. A person having ordinaryskill in the art will readily appreciate that any TDMS drivers may beused in accordance with aspects of the invention.

The DDC signal 28 and CEC bus signal 30 are routed from the port 40 to acontroller 44. The controller 44 controls general operation of the localunit 16. The controller 44 may be any type of controller suitable forhigh speed processing of high quality signals. For example, thecontroller 44 may be a complex programmable logic device (CPLD), ASIC,field programmable gate array, CPU, microcontroller, microprocessor orthe like.

The controller 44 is generally operative to perform all of thefunctionality disclosed herein. For example, the controller 44 iscoupled to port 40, driver 48, RJ45 interface 50, transceiver 52 inorder to multiplex or otherwise combine the TMDS multimedia signals 26along with the DDC and CEC control signals 28, 30 to form an output atport 54, as discussed below.

The controller 44 may also monitor the +5V signal 34. The controller 44selectively makes available the DDC 28 signals (e.g., DDC_SCL andDDC_SDA signals) and CEC 30 signals to transceiver 52. The transceiver52 receives the DDC 28 and CEC 30 signals and outputs correspondingsamples of the DDC and CEC in packet form, as discussed below.

The output of the transceiver 52 is operatively connected to the RJ45interface 50. A detailed representation of RJ45 interface is presentedin FIG. 3.

The DDC signal includes a DDC_SCL (standard clock) signal and a DDC_SDA(serial data) signal. Again, samples of the DDC_SCL and DDC_SDA signalsare output the transceiver 52 and coupled to the output of the RJ45interface 50 via the transformer CT0 as seen in FIG. 3. Samples of theDDC_SCL and DDC_SDA signals are transmitted at a sampling frequencysufficiently high to easily recover the data. An exemplary samplingfrequency may be 550 KHz, for example.

The DDC_SCL and DDC_SDA may be in the form of single bits that may betransmitted in packet form, for example. The packet also may includeadditional data. For example, the packet may contain CEC, IR, USB dataand/or information and the like. The packet containing DDC_SCL andDDC_SDA may be transmitted on two common mode as differential signals.An additional benefit of the present invention is to allow additionalinformation and/or data to be transmitted over the two additional commonmode signals that are available.

Turning next to FIG. 3, a diagram illustrating the use of common modevoltages to transmit digital DDC and CEC signals in packet form isshown. FIG. 3 illustrates the components of the RJ45 Interface 50 thatcombine signals into common mode signals. With reference to FIG. 3,differential HDMI signals (D0, D1, D2 and CLK) are illustrated from topto bottom respectively. The D0− signal and the D0− signal have commonmode choke T0, ferrites F0+ and F0− coupled to the respective D0+ signaland D0− signal. Likewise, D1+ signal and the D1− signal have common modechoke T1, ferrites F1+ and F1− coupled to the respective D1+ signal andD1− signals. The D2+ signal and the D2− signal have common mode chokeT2, ferrites F2+ and F2− coupled to the respective D2+ signal and D2−signal. Finally, the DCLK+ signal and the DCLK signal have common modechoke TCLK, ferrites FC+ and FC− coupled to the respective DCLK+ signaland DCLK− signal. The juncture J0 between the ferrites F0+ and F0− iscoupled to a transformer CT1 with the juncture J1 formed between theferrites F1+ and F1−. Likewise, the juncture J2 between the ferrites F2+and F2− is coupled to a transformer CT0 with the juncture JCLK formedbetween the ferrites FCLK+ and FCLK−. The transformer CT1 and CT0transformers are operable to transmit differential signals having a bitrate minimum of about 200 kbps and a bit rate maximum of about 24 Mbps,for example. One of ordinary skill in the art will readily appreciatethat the values illustrated above are exemplary in nature and notintended to limit the scope of the present invention.

Each transformer CT1 and CT0 is operable to output separate datachannels. The remote unit 20 includes substantially the same circuitryas illustrated in FIG. 3, a discussion of which will be omitted for thesake of brevity. The transformers CT1 and CT0 are coupled to the outputsignals of the RJ45 interface 50 for providing power to the twisted paircable medium. In one embodiment, the power may be applied to the D0 andD1 signal pairs and GND to D2 and DCLK signal pairs through acenter-tapped transformers CT1, CT0 and high frequency ferrites, asdiscussed below. The ferrites may be chosen to handle the maximumcurrent and to provide enough impedance so that the cable medium maystill terminate on approximately 100 Ohms differential impedance, as isconventional. Power can be applied from either end (e.g., the local unit16 or remote unit 20). For example, the local unit 16 may be coupled toan external power source through a power cord, for example, and providepower to the remote unit 20 through the cable medium 18. Alternatively,the remote unit 20 may be coupled to an external power source through apower cord, for example, and provide power to the local unit 20 throughthe cable medium 18.

For purposes of illustration, the voltage applied to the cable mediummay be 24 VDC to allow for the voltage drop on ferrite resistance andcable medium resistance. A high DC voltage is preferred to minimizethese voltage drops by minimizing the DC current that passes through theferrites and cable. Another possible solution is to use an AC voltageinstead of DC voltage.

In one embodiment, the signals output from RJ45 interface 50 may begrouped to form one or more channels. For example, as illustrated inFIG. 2, the D0 and D1 signals form a common mode channel, as they arecoupled to the driver 48. Another common mode channel may be formed fromD2 and DCLK as they are coupled to the transceiver 52. In one embodimentillustrated in FIG. 2, one channel may be used to send DDC information(DDC_SCL and DDC_SDA), hot plug information, CEC information, infraredinformation, +5V signals and emulated USB device data. Another channelremains available for any other data not related to the HDMI signals.For example, the second channel may be used to send stereo-audio in thecase the extender is used as a DVI extender, RS-232 data, etc.

The TDMS multimedia signals and the common mode signals may be output ona single cable medium 18 (shown in FIG. 1), wherein the cable medium 18has a pair of conductors for each of the plurality of signals. Asexplained above, samples of the DDC and CEC signals are transmitted inthe common mode. The HDMI specification states DDC channel maximum bitrate is 100 Kbp. The maximum bit rate for the channels (e.g., channel 1,channel 2) generally will be determined by the delay in the cablemedium. In one aspect of the invention, the extender 10 has beentargeted to work with 300 foot of cable medium, which will introduceabout 900 nanoseconds in round-trip delay. In order to ensure thatDDC_SDA will not change during the time DDC_SCL is high one aspect ofthe present invention is to transmit two DDC_SDA samples, one before andone after DDC_SCL sampling. As shown in FIG. 4, at the remote unit side20, the DDC_SDA and DDC_SCL signals are reconstructed in a manner thatwill assure stable data (e.g., DDC_SDA) while DDC_SCL is high. Thus, thedata at the remote unit 20 will be changed only when the receivedDDC_SCL data is low. This method is presented in FIG. 4.

At Block 302, the sample of DDC_SDA signal is read by remote unit 20.

At Block 304, the DDC_SDA sample read at Block 302 is memorized.

At Block 306, the sample of DDC_SCL is read by remote unit 20.

At Block 308, the remote unit checks if the DDC_SCL signal is low. Ifyes proceeds to Block 310. If not, Block 316 will be executed.

At Block 310, the remote unit 20 will pull the output DDC_CLK low.

At Block 312, the remote unit 20 reads the second sample of DDC_SDA.

At Block 314, the remote unit 20 outputs the value of sample DDC_SDA onits DDC_SDA output.

At Block 316, the DDC_SDA output is forced to mirror the memorizedDDC_SDA value at block 304.

At Block 318, the DDC_CLK output at remote unit 20 is forced to high.

The DDC sampling frequency will be around 550 kHz and the bit frequencywill be 20 Mbps. A packet, from local unit 16 will contain a header andsamples of DDC_SDA, DDC_SCL, and CEC data as a minimum. Likewise, apacket coming from the remote unit 20 will have a different header withdifferent DDC_SDA, CEC data, HP and/or infrared sample data. Latchingfree behavior for DDC signals will be assured by not looping back thereceived low states of DDC_SDA signal. The signal will be converted todifferential signals by a high speed single ended to differentialamplifier (from the transceiver 52) and injected via a center tappedtransformer (CT0) on the common mode of D2 and DCLK pairs. The commonmode signal will be extracted at the remote unit 20, amplified andequalized and then converted back to a single ended signal for use bythe sink 24.

As set forth above, one aspect of the invention relates to transmittingcontrol signals in the form of display data channel (DDC) signals andData (digital audio, USB, CEC, Hot Plug and infrared) as differentialcommon mode signals. In general, there will be two data channels, onedata channel formed from D2 and CLK pairs and the other data channelformed from D0 and D1 pairs. A person of ordinary skill in the art willreadily appreciate that the one or more signal may be carried on anydesired channel.

The HDCP engine uses the DDC channel to communicate between the source12 and the sink 24. The source and sink have to exchange secretencryption keys. These keys are applied to the outgoing and incomingvideo by the HDCP engines in the source and display, respectively. Oncethe exchange and handshaking between the two is done, the source beginsencrypting the video. Starting with the first encrypted frame sent, thesource starts a counter that increments at every frame. The displaystarts its counter with the first encrypted frame received, andincrements it at every subsequent encrypted frame. At a minimum of onceevery 2 seconds, the source requests the counter value from the display.If the display counter value does not match the source counter value,the encryption process starts over and video is interrupted. This is thereason for which a transparent DDC channel is desired.

The signals converted by the local unit 16 are output the port 54 andare transmitted across cable medium 18 to the remote unit 20. The cablemedium 18 is coupled at port 54 through an appropriate connector 18Aconnected to the cable medium. A suitable connector may be a RJ45connector connected on both ends (18A and 18B) of the cable medium 18for connection of the cable medium to the local unit 16 at port 54 andthe remote unit 20 at port 100. The signals output from port 54 includefour pairs of differential signals. The signals are transmitted usingunshielded or shielded Ethernet CAT5, CAT5e, CAT6, CAT7 cable or similarcables that contain at least 4 twisted pairs of conductors. Althoughdisclosed as having RJ45 connectors, one of ordinary skill in the artwill appreciate other suitable connectors may be used in accordance withaspects of the present invention.

Signals from port 54 are routed through cable medium 18 to remote unit20 and received at port 100 through connector 18B. The signals, whichhave been converted to serial data signals are re-constructed at theremote unit 20 for use by the sink 24. In one embodiment, the connector18B may be a RJ45 connector.

Referring to FIG. 5, from port 100 the encoded video signals routed to acoupler 102. The coupler 102 may be an AC coupler, which removes DC biasassociated with the received signals. The output of the coupler 102 maybe received by a driver 104. The driver 104 may be a TMDS Equalizer. Ingeneral, the coupler 102 receives four differential pairs of signals.The output of the driver 104 are high speed differential video signals(e.g., D0, D1, D2 and DCLK, as discussed above for output the port 106and input into the sink 24 (FIG. 1). One goal is to re-create thesignals output from the driver 104 to correspond, as close as possibleto the signals 26 output from the source 12.

The common mode signals transmitted through the cable medium are decodedat the receiver 108 and input to the controller 110. The controller 110may be an identical controller to controller 44, discussed above. Oncedecoded, the control signals may be routed to the controller 110 andselectively output the port 106 by the controller 110 for use by thesink 24.

From port 106, high definition multimedia signals (e.g., HDMI, DVIsignals) are output to a coupler 22. Coupler 22 is connected to the port106 and the display 24 (or other sink device) to facilitatecommunication between the source 12 and the display 24. The coupler 22may be, for example, an HDMI cable, a DVI cable, etc, for connecting theremote unit to the display 24 (or other sink device). The coupler 22 hasconnectors 22A, 22B that matingly engage with port 106 and/or inputassociated with the display 24.

As shown in FIG. 5, the remote unit 20 further includes a transceiver112 for transmitting control data back to the local unit 16 and/orsource 12 through the port 100 and cable 18. Like transceiver 52(discussed above), transceiver 112 converts the single-ended controlsignals to differential control signals for output to the local unit 16through cable medium 18. Such mechanism allows for HDPC complianceprocedures. Thus, the local unit 16 and the remote unit 20 work togetherto ensure transparent DDC communication between the source and/or sink.

Since the display 24 may be up to 300 feet away from the source 12, itis desirable to have an infrared receiver 114 coupled to the controller110 in order to allow the user to control the source 12 while present ator near the sink 24 (e.g., a display). Therefore, the local unit 16 andthe remote unit 20 are also operable to exchange infrared signals.Accordingly, the remote unit 20 may optionally include a receiver 114.The receiver 114 may be coupled to the controller 110 and receivessignals from a remote control (not shown), for example. As such, thereceiver 114 may receive infrared signals that may be encoded on atwisted pair of conductors and routed through the port 100 to the localunit 16 and transmitted to the source 12 in order to control one or morefunctions of the source 12, in a similar manner as described withrespect to the control signals (e.g., through common mode signaling).The receiver 114 may be connected to the remote unit 20 through a 3.5 mmstereo jack or other suitable interface, for example.

For satisfactory end-user results, the receiver 114 should be mounted tothe edge of the sink device 24 (e.g., display) with the IR window of thereceiver 114 facing the user (the same direction as the display screen).The IR data is transmitted over the common mode of D2 and DCLK, asdiscussed above with respect to the HDMI signals. Once the IR data hasbeen received at the local unit 16, it is converted by the controller 44and transmitted out transmitter 60 to the source 12. Based on thisrelationship the transmitter 60 should be mounted such that the LED ofthe transmitter is in the direct line of sight of the IR window of thesource 12.

Referring back to FIG. 2, optional support for stereo audio allows theuser to extend audio from a DVI source to a DVI or HDMI display. Analogstereo audio signal may be received at the local unit 12 from an analogstereo audio source (not shown) at port 70. The user may choose betweenanalog or digital (e.g., S/PDIF) audio signals to be extended. The localunit 12 may sense if digital audio signal are applied and switch to adigital mode, if appropriate. The local unit 12 will also send a controlbit to the remote unit 20, so that the remote unit will switch to thedigital mode, if appropriate. The stereo audio signal may be convertedto a digital signal by an analog to digital (ND) converter 72. Theconverted data or the digital audio data is then sent to the controller44 wherein data flow is controlled. The controller 44 selectivelyoutputs the audio data to the driver 48, which converts the single-endedsignals to differential signals for output over the channel formed bythe common mode corresponding pair of D0 and D1 and output port 54, asillustrated in FIG. 2.

In addition, the controller 44 may send and receive command and controlinformation to and from the controller 110 of the remote unit 20 via oneof the two data channels or both.

The remote unit 20 receives the stereo audio signal at the interface100, after which the stereo audio signal passes to the receiver 108 andcontroller 110. The controller 110 functions in a manner similar to thedata controller 44 and multiplexes/demultiplexes the stereo audiosignal, for example. The stereo audio signal is output to the audio port120 if digital audio is implemented or the stereo audio signal isconverted from a digital signal to an analog signal by a digital toanalog (D/A) converter 116. After being converted to an analog signal,the stereo audio signal preferably corresponds to the stereo audiosignal received by the local unit 102 and is transmitted to a stereoaudio device, such as a stereo receiver, with the same voltage as thestereo audio signal received by the local unit 20.

Referring to FIGS. 6 and 7, a local unit 16 and a remote unit 20 areillustrated, respectively. The local unit 16 and the remote unit 20 aresubstantially similar to local unit 16 and remote unit 20 illustrated inFIGS. 2 and 5, respectively, except that circuitry for the exchange ofemulated USB signals and RJ45 are also illustrated. For example, withrespect to the local unit 16, a RJ45 port 130 and USB port 132 are alsoavailable. The RJ45 port 130 is coupled to a RS232 driver 134, which iscoupled to the controller 44 to facilitate the exchange of RS232 databetween the local unit 16 and the remote unit 20. Furthermore, USB port132 is coupled to a USB HUB 136 which is coupled to a primarymicrocontroller 138 and a secondary controller 140. The controllers 138and 140 are coupled to the controller 44 to facilitate the exchange ofUSB data between the local unit 16 and the remote unit 20. Furthermore,driver 48 (FIG. 2) is replaced with transceiver (142) to facilitatetwo-way data exchange.

Referring to the remote unit 20 illustrated in FIG. 7, a RJ45 port iscoupled to a RS232 driver 154, which is coupled to the controller 110 tofacilitate the exchange of RS232 data between the local unit 16 and theremote unit 20. USB ports 156 are coupled to a USB Hub 158 andmicrocontroller 160, which are ultimately controlled by the controller110 to facilitate the exchange of information between the local unit 16and the remote unit 20. The emulated USB signals are sent as describedpreviously on the common mode of D2 and DCLK pairs and Stereo Audio andRS232 signals are sent in the same manner on the common mode of D0 andD1 pairs.

An exemplary method 200 for extending high definition multimedia signalsover a single twisted pair cable having a plurality of twisted pairconductor will now be discussed. High-definition content is generallyprotected by encoding/decoding the video signals according to the HDCPspecification.

At power on, the local unit 16 will generally not present itself to thevideo source 12. Instead the hot plug input 32 will be kept low untilcommunication with remote unit 20 is established and the sink is poweredon at which moment the hot-plug signal is driven high. Upon power on,the EDID table is read via the DDC channel, as discussed above.

While the hot plug signal 32 is driven low the source 12 will not outputTMDS video data to the local unit 16. The method 200 is described ingeneral terms below and assumes that the necessary handshaking betweenthe source 12 and the sink 24 have already occurred. Additional detailsregarding steps performed in method 200 are discussed above.

At block 202, a plurality of differential multimedia signals arereceived from a source 12 at the local unit 16. The multimedia signalsmay be HDMI or DVI signals, for example. HDMI signals generally includea plurality of video signals and a clock signal.

At block 204, the plurality of differential multimedia signals aretransmitted to the remote unit 20.

At block 206, the data display channel (DDC) communication isestablished between the local unit 16 and the remote unit 20. The DDCinformation, which includes serial clock data and serial data, issampled and transmitted in packet form at a rate sufficient to complywith high-bandwidth digital content protection (HDCP). The DDCinformation is then transmitted as a differential common mode signalcorresponding to at least two of the plurality differential multimediasignals.

At block 208, the plurality of differential multimedia signals and theDDC information is received at the remote unit 20. The remote unit 20generally decodes the received signals.

At block 210, the remote unit 20 transmits DDC information from theremote unit to the local unit. This is done over the common mode, asdiscussed above.

At block 212, the plurality of differential multimedia signals areoutput from the remote unit to an associated sink 24 (e.g., a display)based at least in part on the control information exchanged between thelocal unit and the remote unit.

While for purposes of simplicity of explanation, the methods illustratedherein include a series of steps or functional blocks that represent oneor more aspects of the relevant operation of the extender 10, it is tobe understood and appreciated that aspects of the present invention arenot limited to the order of steps or functional blocks, as some steps orfunctional blocks may, in accordance with aspects of the presentinvention, occur in different orders and/or concurrently with othersteps or functional blocks from that shown and described herein.Moreover, not all illustrated steps or functional blocks of aspects ofrelevant operation may be required to implement a methodology inaccordance with an aspect of the invention. Furthermore, additionalsteps or functional blocks of aspects of relevant operation may be addedwithout departing from the scope of the present invention.

Although aspects of the invention have described in the context ofhardware circuitry, as used herein the term “circuitry” means hardwareand/or software to perform a claimed function.

Specific embodiments of an invention are disclosed herein. One ofordinary skill in the art will readily recognize that the invention mayhave other applications in other environments. In fact, many embodimentsand implementations are possible. The following claims are in no wayintended to limit the scope of the present invention to the specificembodiments described above. In addition, any recitation of “means for”is intended to evoke a means-plus-function reading of an element and aclaim, whereas, any elements that do not specifically use the recitation“means for”, are not intended to be read as means-plus-functionelements, even if the claim otherwise includes the word “means”.

What is claimed is:
 1. A method for extending high definition multimediasignals over a single twisted pair cable medium between a source and adisplay, the single twisted pair cable medium having a plurality oftwisted pair conductors, the method comprising: receiving a plurality ofsource differential multimedia signals and control information from thesource at a local unit, wherein the plurality of source differentialmultimedia signals include a plurality of source video signals and asource clock signal; generating a plurality of local unit differentialmultimedia signals at the local unit based on the plurality of sourcedifferential multimedia signals, the plurality of local unitdifferential multimedia signals including a plurality of local unitdifferential video signal pairs and a local unit differential clocksignal pair; converting at least a portion of the control informationinto converted data display channel (DDC) information at the local unit;transmitting the plurality of local unit differential video signal pairsand the local unit differential clock signal pair from the local unit toa remote unit over a first channel and a second channel, the firstchannel comprising a first conductor pair and a second conductor pair ofthe plurality of twisted pair conductors of the cable medium and thesecond channel comprising a third conductor pair and a fourth conductorpair of the plurality of twisted pair conductors of the cable medium;transmitting the converted DDC information from the local unit to theremote unit as a differential common mode signal over the first andsecond conductor pairs of the first channel; powering one of the localunit and the remote unit through the first and second channels, thefirst and second conductor pairs of the first channel being coupled to afirst voltage and the third and fourth conductor pairs of the secondchannel being coupled to a second voltage, the second voltage beingdifferent than the first voltage; receiving the plurality of local unitdifferential multimedia signals and the converted DDC information at theremote unit; extracting the converted DDC information at the remote unitfrom the first channel; generating reconstructed DDC information at theremote unit from the converted DDC information; generating a pluralityof remote unit differential multimedia signals at the remote unit basedon the received plurality of local unit differential multimedia signals;and outputting the plurality of remote unit differential multimediasignals and the reconstructed DDC information from the remote unit tothe display based at least in part on the control information.
 2. Themethod of claim 1, further comprising: transmitting return remote unitDDC information from the remote unit to the local unit over the firstchannel.
 3. The method of claim 1, wherein transmitting the plurality oflocal unit differential video signal pairs and the local unitdifferential clock signal pair from the local unit to a remote unit overthe first and second channels comprises: transmitting a first local unitdifferential video signal pair of the plurality of local unitdifferential video signal pairs over the first conductor pair of thefirst channel; transmitting the local unit differential clock signalpair over the second conductor pair of the first channel; transmitting asecond local unit differential video signal pair of the plurality oflocal unit differential video signal pairs over the third conductor pairof the second channel; and transmitting a third local unit differentialvideo signal pair of the plurality of local unit differential videosignal pairs over the fourth conductor pair of the second channel; thefirst, second and third local unit differential video signal pairs beingdifferent signals.
 4. The method of claim 1, further comprising:converting additional data into additional differential common modesignals at the local unit for transmission to the remote unit; andtransmitting the additional differential common mode signals as adifferential common mode signal over the third and fourth conductorpairs of the second channel.
 5. The method of claim 4, furthercomprising: using a first local unit transformer in the local unit and afirst remote unit transformer in the remote unit for communicating thedifferential common mode signals between the local unit and the remoteunit over the first and second conductor pairs of the first channel; andusing a second local unit transformer in the local unit and a secondremote unit transformer in the remote unit for communicating thedifferential common mode signals between the local unit and the remoteunit over the third and fourth conductor pairs of the second channel. 6.The method of claim 5, further comprising: coupling a first local unitpower terminal of the local unit to a center tap of the first local unittransformer; coupling a first remote unit power terminal of the remoteunit to a center tap of the first remote unit transformer; coupling asecond local unit power terminal of the local unit to a center tap ofthe second local unit transformer; coupling a second remote unit powerterminal of the remote unit to a center tap of the second remote unittransformer; and powering both the local unit and the remote unit byconnecting the first and second voltages directly to the first andsecond local unit power terminals or by connecting the first and secondvoltages directly to the first and second remote unit power terminals.7. The method of claim 1, further including transmitting audio signalsfrom the local unit to the remote unit over the first or second channel.8. The method of claim 1, further including transmitting emulateduniversal serial bus data over the first or second channel.
 9. Themethod of claim 1, further including transmitting infrared signals fromthe remote unit to the local unit over the first or second channel. 10.The method of claim 1, wherein converting at least a portion of thecontrol information into converted data display channel (DDC)information comprises converting at least a portion of the controlinformation into clock data and serial data; and transmitting theconverted DDC information from the local unit to the remote unitcomprises sampling and transmitting the converted DDC information inpacket form at a rate sufficient to comply with high-bandwidth digitalcontent protection (HDCP).
 11. An extender for extending high definitionmultimedia signals over a single twisted pair cable medium between ahigh definition video source and a video sink, the single twisted paircable medium having a plurality of twisted pair conductors, the extendercomprising: a local unit comprising: a first local port for receivinghigh definition multimedia signals and source control information fromthe high definition video source, wherein the high definition multimediasignals include a plurality of video signals and at least one clocksignal; a second local port for receiving the twisted pair cable medium;first local circuitry for generating a plurality of differential videosignal pairs based on the high definition multimedia signals; secondlocal circuitry for converting at least a portion of the source controlinformation into data display channel (DDC) information; third localcircuitry for transmitting a first two differential video signal pairsof the plurality of differential video signal pairs on a first channeland transmitting the DDC information as a differential common modesignal on the first channel with the first two differential video signalpairs, and for transmitting a second two differential video signal pairsof the plurality of differential video signal pairs on a second channelout of the second local port over the twisted pair cable medium, thefirst channel comprising a first two conductor pairs of the plurality oftwisted pair conductors and the second channel comprising a second twoconductor pairs of the plurality of twisted pair conductors of the cablemedium, none of the twisted pair conductors of the second channel beingpart of the first channel; a first local unit power terminal coupled tothe first channel; and a second local unit power terminal coupled to thesecond channel; a remote unit comprising: a first remote port forreceiving the twisted pair cable medium including the first and secondchannels; first remote circuitry for converting the first twodifferential video signal pairs and the second two differential videosignal pairs received at the first remote port into a plurality ofremote high definition multimedia signals; second remote circuitry forextracting the DDC information from the differential common mode signalreceived at the first remote port on the first channel; third remotecircuitry for reconstructing the DDC information from the extracted DDCinformation to provide remote display control information; a firstremote unit power terminal coupled to the first channel; and a secondremote unit power terminal coupled to the second channel; a secondremote port coupled to the first and third remote circuitry foroutputting the plurality of remote high definition multimedia signalsand the remote display control information to the video sink; whereinpower is provided to one of the local unit and the remote unit throughthe first and second channels by coupling first and second voltages toone of the first and second local unit power terminals or the first andsecond remote unit power terminals, the first and second voltages beingdifferent.
 12. The extender of claim 11, the second local circuitryconverts at least a portion of the source control information into DDCinformation including clock and serial data for sampling andtransmitting in packet form as a differential common mode signal at arate sufficient to comply with high-bandwidth digital content protection(HDCP).
 13. The extender of claim 11, wherein common mode communicationsbetween the local unit and the remote unit is conducted over the secondchannel.
 14. The extender of claim 13, wherein the first channelexchanges the DDC information and the second channel exchanges audioinformation between the local unit and the remote unit.
 15. The extenderof claim 13, wherein the first or second channel is utilized to transmitUSB data.
 16. The extender of claim 13, wherein the first or secondchannel is utilized to transmit infrared signals between the local unitand the remote unit.
 17. The extender of claim 13, further comprising: afirst local unit transformer in the local unit and a first remote unittransformer in the remote unit for communicating the differential commonmode signals between the local unit and the remote unit over the firstchannel; and a second local unit transformer in the local unit and asecond remote unit transformer in the remote unit for communicating thedifferential common mode signals between the local unit and the remoteunit over the second channel.
 18. The extender of claim 17, wherein: thefirst local unit power terminal is connected to a center tap of thefirst local unit transformer; the first remote unit power terminal isconnected to a center tap of the first remote unit transformer; a secondlocal unit power terminal is connected to a center tap of the secondlocal unit transformer; and a second remote unit power terminal isconnected to a center tap of the second remote unit transformer; whereinpower is provided to one of the local unit and the remote unit throughthe first and second channels by coupling the first and second voltagesto one of the first and second local unit power terminals or the firstand second remote unit power terminals.
 19. The extender of claim 18,wherein a DC or an AC voltage is applied to one of the local unit powerterminals and the remote unit power terminals to power the local andremote unit using the first and second channels of the twisted paircable medium.
 20. The extender of claim 18, wherein one of the firstlocal and remote unit power terminals is connected to a first voltage,and one of the second local and remote unit power terminals is connectedto ground to power the local and remote units using the first and secondchannels of the twisted pair cable medium.